Apparatus for the production of electrical oscillations



April 1938. A. H. MIDGLEY 2,112,921

APPARATUS FOR THE PRODUCTION OF ELECTRICAL OSCILLATIONS Filed March 22, 1937 3 Sheets-Sheet l April 5, 1938. A H M|DGLEY 2,112,921

APPARATUS FOR THE PRODUCTION OF ELECTRICAL OSCILLATIONS Filed March 22, 1937 3 Sheets-Sheet 2 April 5, 1938. A. H. MIDGLEY 2,112,921 I APPARATUS FOR THE PROI DUCTION OF ELECTRICAL OSCILLATIONS Filed March 22, 1937 3 Sheets-Sheet 3 IN VEN TOR.

emf Mz'qigle Patented Apr. 5, 1938 PATENT OFFICE APPARATUS ELECTRICAL FOR THE PRODUCTION OF OSCILLATIONS Albert Henry Midgley, Wembley, England Application March 22,

1937, Serial No. 132,435

In Great BrltaimSeptember 23, 1935 4 Claims.

Thisinvention relates to apparatus for generating electrical oscillations or an undulating potential by electrostatic means more particularly for use in apparatus designed to produce by all electric means any musical notes or combinations of the'same such as might be produced by an organ or like instrument.

The invention has particular reference to-such apparatus of the kind employing a plurality of ring-shaped members of undulating or sine wave formation movable relatively to an electrode or electrodes in close proximity thereto, a difference of static potential being maintained between the members and the electrode or electrodes in order to generate an undulating potential electrostatically. One such form of apparatus is described in Patent No. 2,032,044, February 26, 1936.

In such apparatus each ring-shaped member and the electrode constitute the plates of a condenser, the capacity of which is varied in order to generate the undulating potential or electrical oscillations by the relative movement producing a variation in the effective plate area of the condenser, and the undulating potential or electrical oscillationsare converted into sound waves by means of an amplifier and loud speaker.

In such apparatus as hitherto proposed the effective plate area is relatively small with the result that the working capacity is small and the impedances of the associated circuits must be of a high order and thus the leakage losses are great and the power generated is small.

The object of the present invention is. to improve upon existing apparatus by obtaining a greatly increased capacity thus reducing the loss and increasing the power generated.

The invention consists in apparatus of the kind referred to for-the production of electrical oscillations characterized in this that the, or each, electrode is also the sine wave or of undulating or zig-zag form.

Further features of the invention will be apparent from the description given hereafter.

The accompanying drawings illustrate several modes of carrying out the invention.

Figure 1 shows in elevation one-half of a convenient form of ring member and disc.

Figure 2 is a view showing two members of the form shown in Figure 1 displaced 180 out of phase relatively to one another.

Figures 3 and 4 are similar views to Figures 1 and 2 but showing a different form of ring member.

ing a third form of ring member.

Figures 5 and 6 are again similar views show- Figure '7 is an axial section of a structural form of the condenserincluding a diagram of the fundamental connections thereto for generating a partial note.

In carrying my invention into effect in one convenient manner I may proceed much in the manner described in Patent No. 2,032,044 by providing a stationary circular disc l0 of insulating material, to the face of which is fixed a number of concentric rings ll of conducting material, the inner and outer edges of which may be of undulating or sine wave formation as shown in Figure 1.

There is provided one such ring for each semitone of the musical scale and the total number of rings provided will be dependent on the number of octaves of the musical scale which it is desired to reproduce, the number of undulations of successive rings progressing geometrically in the ratio of approximately 1 to W which is the interval of a semi-tone.

Referring to Fig. 7 there is shown a second disc iii of insulating material having concentric ring members I I of conducting material of exactly the same number, construction and formation, as those of the first disc, which is adapted to be rotated by the shaft II. The axis of each disc is in alignment and the disc i0 is mounted so that the radial surfaces of the sets of ring members on the respective discs are in close proximity and a difference of static potential is maintained between the members by any suitable means. The apparatus may be completed by connecting the members to a keyboard and stop keys and in the manner as diagrammatically illustrated in Fig. 7 and described in the beforementioned specification. In other words, the secondary of the condenser is connected to a common amplifier which supplies a loud speaker l1 and when one of the undulating rings H in inductive relation to the secondary element is. connected to a source of current an undulating potential will be electrostatically induced in the secondary element at a frequency depending on the speed of rotation of the shaft l4 and the distance separating the undulations of the ring i I. This undulating potential is applied to an amplifier l6 and a musical note will be emitted from the loud speaker I1 the pitch of which depends on the frequency and the intensity thereof depends on the potential to which the ring is subjected. The source of potential may be any suitable source and the connection of the ring II to the source is made by the medium of a bus bar l8 which is adapted to be connected to a primary ring by means of a contact l9 carried on a key 20 and adapted to be connected to the source by means of a contact 2!] carried on a stop 22 of an organ. Each contact I!) is connected to a ring ll through an adjustable resistance 23 and a resistor 24 so that each ring may be suificiently charged from the source by manual engagement of the organ keys 20.

Considering, for example, Figures 1 and 2, Figure 1 may be taken as showing two ring members exactly in phase while Figure 2 indicates the same two ring members displaced out or phase relatively to one another, and it will be seen that the effective condenser plate area is a maximum in Figure 1 and is a minimum in Figure 2, and the difference between the minimum and maximum condenser plate areas is relatively large and therefore the working capacity and the power generated are both greatly increased as compared with known constructions so that the associated impedances may now be of a much lower order than those hitherto considered necessary and thus the leakage losses will be considerably reduced.

Instead of making both the inner and outer edges of the ring member of sine wave or undulating formation the outer edge only may be so formed as shown by the ring Ha in Figures 3 and 4 or, alternativelmthe inner edge only may be of such formation. I may also shape the edges of the ring member in such a manner that each pair of associated ring members may produce a tone containing more than one partial, one such form of ring member no being shown in Figures 5 and 6.

Moreover in any modification of the invention each stationary ring member may be divided into sections of a circle insulated from one another and the sections of each diametrically opposite pair may be connected together so that a different static potential may be maintained between the difllerent sections and the corresponding rotating member as described in Patent No. 2,032,044.

Alternatively, the movable ring members may be so constructed in sections if associated with some suitable form of slip ring, commutator, or like construction to enable the necessary connections to be made.

I claim:

1.. In an electrical musical instrument, an electrostatic generator adapted for the production of electrical oscillations comprising two relatively rotatable electrodes arranged in electrostatically inductive relation, both of said electrodes consisting of rings of undulating form.

2. Apparatus according to claim 1 characterized by having each edge of both electrode rings of sine wave form.

3. Apparatus according to claim 1 characterized by the fact that the edges ofi each ring member are so shaped that a corresponding pair of ring members may produce a tone containing more than one partial.

4. Apparatus according to claim 1 characterized by the fact that the ring member constituting one electrode of the condenser and the associated electrode oi" the condenser are of identical sine wave iorrn.

ERT Y MlDGlL-EY. 

